1. Field of the Invention
The invention relates to an abrasion resistant photocurable acrylic coating composition that can provide good adhesion to subsequent coatings deposited thereon, and a hard coated article, especially an optical article such as an ophthalmic lens, comprising a substrate coated with a coating obtained from the above abrasion resistant acrylic coating composition providing good subsequent adhesion.
2. Description of Related Art
It is a common practice in the art to coat at least one main surface of a lens substrate, such as an ophthalmic lens, with several coatings for imparting to the lens substrate additional or improved optical or mechanical properties. These coatings are designated in general as functional coatings.
Thus, it is usual practice to coat at least one main surface of a lens substrate, typically made of an organic material, with successively, starting from the surface of the lens substrate, an abrasion—and/or scratch-resistant coating (hard coat), an anti-reflection coating and an antifouling top coat.
The coatings deposited above the abrasion and/or scratch resistant coatings must have a good adhesion, whatever their deposition process is.
Photocurable acrylic coatings, especially UV curable acrylic coatings used as anti-abrasion coatings are known in the art.
The interest of acrylic coatings in general is that they can be polymerized in a short amount of time.
However, the problem associated with these UV curable acrylic coatings is that it is difficult to get a good adhesion of subsequent coatings deposited thereon.
This problem is especially crucial when the subsequent coatings are sol/gel antireflective coating compositions applied by spin or dip process.
Present commercial UV curable coatings range in wetting properties from fair to very poor and exhibit poor adhesion to coatings that are spin coated onto their surface unless some type of surface treatment is used prior to the application of subsequent coatings.
Acrylic coatings are well known. For example, U.S. Pat. No. 6,100,313 describes a UV curable abrasion resistant coating composition having good tintability and abrasion resistance at the same time.
The coating composition described in this patent is substantially free of volatiles and comprise at least 10% by weight, solids basis of the hydrolysis product of an epoxy-functional alkoxysilane, a polymerizable ether selected from the group consisting of glycidyl ethers, allyl ethers and vinyl ethers and an ethylenically unsaturated monomer other than said polymerizable ether.
U.S. Pat. Nos. 6,780,232 and 7,037,585 also describe similar UV curable coating compositions comprising the hydrolysis product of an epoxy-functional alkoxysilane, an unhydrolyzed epoxy-functional alkoxysilane, an ethylenically unsaturated monomer. The ethylenically unsaturated monomer is generally an acrylate monomer. The required acrylate has an acrylate functionality not greater than 2.
The main technical problem addressed by these patents is to get a tintable hard coating.
There is no mention of a particular specific problem linked to adhesion problems of susbsequently applied coatings.
Accordingly there is still a need of providing photocurable, preferably UV curable abrasion resistant compositions solving such problems.